We are using WCF Custom Channel: DuplexHttp (from MSDN - http://code.msdn.microsoft.com/duplexhttp) to have a thick .NET client connect to our WCF service with callbacks.
We have noticed that although the throughput is good, the maximum number of clients connected to the server seems to top out at about 60-70, which isn't good at all. This is even if the client is calling a one-way operation on the service contract that has callbacks.
The same test run with BasicHTTP and no callbacks/sessions seems to perform fine (1600+ simultaneous client connections).
I've tried tweaking all of the associated configs, but with no luck. I've also tried stripping out the first two binding elements of the DuplexHttpBinding (the polling and session elements), essentially leaving it as a standard BasicHTTPBinding, and the maximum connections numbers goes up to expected values (1600+ again)...so the problem must be in/associated with the HttpPollingBindingElement or the HttpSessionBindingElement...I think.
Anyone out there familiar with this technology or have any ideas?
Thanks in advance!